Processing samples

Tiny crabs seived from mangrove leaf litter.

We came back from 2 days in the mangroves with bags of leaf litter and muck scooped from the base of the trees, bags of old and not so old dead wood, captured spiders, crabs, insects, snails, and floating plant matter like turtle grass and mangrove propagules.  All of these samples have to be processed when we get back to the lab. Some need to be dried or frozen, and the rest require careful sorting and examination.  For leaf litter, we wash and sieve out the small particles, and examine it closely to find any animals that live in this environment.  We pick through sieves and trays of wet leave debris to record and capture tiny marine creatures, such as crabs, amphipods and isopods, polychaete worms, and small snails. 

The dead wood is stripped of bark, then broken open to search for insects that bore into the wood and use it to lay eggs or to live out their larval stages.  We are finding centipedes, solitary green bees, various larvae and black ants. Those are the most difficult to sample. They try to escape from the sample tube every time I open it to add another! 

Why do we do this? The trees we are sampling are part of an experiment to see which nutrients are available in the natural environment and which are less common. The trees are in three groups - Control (natural, no fertilizer), Nitrogen, and Phosphorus.  N and P both occur in the marine environment but not in equal amounts; the lesser of the two may be the “limiting nutrient,” meaning that tree growth is limited by the availability of that nutrient.  Adding more of a nutrient is a way to see if it makes a difference in tree growth. Sampling the critters allows us to measure how nutrient enrichment may be trasferred through the mangrove ecosystem (at least of the treated trees) and how that affects the productivity and diversity of other organisms that utilize everything from submerged roots to high branches.